Prior art workers have devised many types of fastener driving tools. As used herein and in the claims, the term "fastener" is to be considered in the broadest sense, referring to substantially any fastener capable of being driven into a workpiece. Examples of such fasteners are pins, brads, headed nails, finishing nails, staples, and the like.
Perhaps the most common form of fastener driving tool is a pneumatically actuated tool. Prior art workers have developed a multiplicity of pneumatically actuated fastener driving tools to a very high degree of safety and sophistication.
More recently, there has been considerable interest in electro-mechanical fastener driving tools utilizing a solenoid mechanism or a fly wheel mechanism to drive the fasteners. Electro-mechanical fastener driving tools are of particular interest for use where a source of compressed air is not available.
The fastener driving tools thus far described are of the single blow variety, wherein the fastener is driven home by a single impact of the tool driver. Such tools are well adapted for industrial use, but they tend to be large, bulky and heavy. Therefore, they are not as well suited for home use, light industrial use or the like.
In light of the above, prior art workers, with an eye to light industrial applications and home uses, have also turned their attention to multiple blow fastener driving tools wherein simple rotary motion, obtained from an appropriate prime mover, is converted to linear reciprocating motion of a driver. Such tools have a number of advantages. First of all, they can employ a low power prime mover. As a result of the reduced power that must be dissipated, as compared to single blow tools, the multiple blow tools are characterized by reduced sound levels. Finally, such tools can be of less complex, more compact and lighter weight construction than the usual single blow tool.
Despite these advantages, multiple blow tools, to date, have not been highly successful in the marketplace. Generally, prior art multiple impact tools have fallen into two basic categories. The first encompasses those tools which accomplish translation of rotary motion into reciprocating motion through the use of some form of eccentric or crank shaft. The second category encompasses those multiple impact tools which employ some form of cam profile for translation of rotary motion to reciprocating motion. The tools of the first category, employing an eccentric or crank shaft for motion translation, accomplish the translation in a very smooth manner, but with a low and diminishing velocity.
Those prior art multiple impact tools which translate rotary motion into reciprocating motion through the use of some form of cam profile address the problem of attaining velocity in one of two ways. A first method is to develop a cam profile which maximizes velocity to the point of reversal of the reciprocating motion. However, the motion translation achieved is not very smooth. The other method is to use a form of cam profile to precondition the drive cycle which is performed by some other power source such as a spring. This approach generally requires an abrupt release by the cam of the other power source (i.e. the spring) in order to release the drive power. This produces high wear on the cam surface. The present invention constitutes an improvement of this general type of multiple impact tool eliminating prior art problems therewith.
It is an object of the present invention to provide a system wherein a cam wheel lifts a hammer and compresses a spring, the spring transferring energy to the hammer and thence to a driver with little or no wear imparted to the cam wheel.
It is an object of the present invention to provide a system wherein the direction of the drive energy is in line with the direction of the nail.
It is an object of the present invention to provide a magazine which shifts vertically between and extended position and a retracted position.
It is an object of the present invention to provide a guide and biasing assembly for the magazine to guide its vertical movement while maintaining its proper orientation and for biasing the magazine to its extended position.
It is an object of the present invention to provide a multiple impact tool with means to control the depth of drive.
It is an object of the present invention to provide a battery powered multiple impact tool which conserves energy by automatically turning off the motor when the magazine is in its uppermost position and when the magazine is in its lowermost position, or when a fastener is fully driven.
It is an object of the present invention to provide an electric multiple impact tool wherein the amount of energy consumed during a drive cycle depends upon the hardness of the workpiece and the force applied by the operator.
It is an object of the present invention to provide an electric multiple impact tool wherein the number of cam rotations per drive cycle can be varied.